Treatment of deep wells



Patented Sept. 13, 1932 UNITED STATES PATENT ounce:

JOEE film urn 1088!. M031), mmn, IICHIGAH, ASBIGNOBS TO THE 139W cannon. conm, OI mum), 110316, A CORPORATION 01' HICHIGAH ma'rhin'ornmwmms- Drawing.

The ment 0 deep wells, such as oil, gas, brine or water wells, to increase the output therefrom. It is more ially concerned with the 5, treatment of w in which the mineral-bearing stratum consists of a limestone or other ca careous formation, or is contiguous to such a formation.

An object of the invention is to counter- 1 act some preventable natural causes for the decline of yield of a well. A familiar example is the decline of production of an oil well. When it is first drilled into an oilstratum, the release of pressure u n 35 then epositmay causethewellto ow naturall or a certain length of time. The flow gradually reeede from the initial high point to the point where natural flow does not produce a sufiicient yield, and thereafter pumpigguvlvill be resorted to, until the continued d e in on ut renders further operation unprofitable. many cases, however, the stoppage .of oil output is caused, not by exhaustion of the oil supply but by the building up of solid deposits 0 wax or the like in the channels an pores of the 0.3.- bea rock which obstruct and finally ma out o altogether the flow of oil to the we Various methods has been ugendlfolr open}; 3 mgu orcleanmg a oggedw oe,suc as dri'lling, shooting with explosive or b chemical treatment. The first two methodi mentioned have the disadvantage that the pump rod and tube must be remcved prior toapl thetre'atmenhinadditioiito which, 3% case of an explosive, there sdangerof ecasing. The

chemical methods heretofore proposed have either notbeen found efi'ective to clear the 4.0 hole or they-have involved the use-of corrosive ces which metal parts of the well structure.

Asan illustrati -a chemical method is describedinU iited tatesPatent 556,669,- ei cordingtowluchtbeflowofanoilwellina 7 injurious to the Application fled has 80, 10 88. lertal Io. 620,388.

resent invention relates to the treatlimestone formation is increased by treating with aguantity of an acid, such as hydrochloric aci The acid has the effect of attacking and dissolving the rock, thereby enlarging the cavity at the bottom of the well, or the channels and pores in the rock through which oil flows to the well.. In actual practice, however, this method has never been generall adopted, due to the fact that the acid attac the metallic casing, pump tube, etc. about as actively as the rock, and causes serious damage thereto.

We have now found that the last-mentioned method may be adapted for use in increasingbor restoring the flow .of oil wells by snita le modification without material injury to the casing or other metallic-parts of the well. The treatment can be carried out at less cost and with better results than any of the methods heretofore em loyed. The invention, then consists of. t e improved method hereinafter fully described and particularly pointed out in the claims.

In ca out our improved method we employ a mineral acid, referably hydie w chloric acid, inasmuch as e latter upon reacting with the calcareous rock forms watersoluble salts which remain in solution and are removed from the well with the spent acid. To the acid we add a small amount of a substance capable of inhibit attack of the acid upon metal surfaces, e. g. 0 iron or steel, co per, e with which it comes in contact. the inhi iting agent we prefer to use an arsenic compound soluble in the acid solution, in exam les of which are arsenic acid, ELMO arsenic trioxide, As,0,, or a soluble arsenate or arsenite, such as the corresgionding alkali metal salts. The amount 0 arsenic comd added may be varied, but we have ound that from 1 to 5 per cent thereof, based upon the weight of the solution, will be satisfor the purpose. Other inhibitors which may be used are anides, Organic nitrogen bases'such as e, phenyl-hydre, 9e

BEST AVAlLABLE COPY I With such strength of acid the corrosive acbe intr tube, so that the latter need not be with rawn tion thereof upon metals, particularl iron or steel can be lar 1y or substantia y inhibited by adding t ercto a relatively small amount of an arsenic compound or other inhibitin agent. Consequently, the acid can iluced into the well through the ump prior to the treatment; It is suflicient merely to pull the ump rod and valves, and to pour the acid so ution into the well throu h the tube. Due to the resence of the i ibitor there will be no su antial attack upon the pump'tube, or upon the well casing if the charge of acid rises high enough in the well to contact with thecasing.

The acid solution is referably dded in amount calculated to the bore the well to a depth not ex the thickness of the mineral-bearing stra um. In order to force the charge of acid out of the pump tube into the bore of the well against t e head of oil standing in the hole, it may be followed by a charge of oil, water or other liquid suiiicient to overcome the head or pressure may be applied by other suitable means, ewg hby airpressure orbymeans ofa ump. en introduced into the bottom the well, the aiti-3w? ti i sli or 1 ere y argmg poresandc annelsintheroc ore mn u new channela The action o f the gid n K a limestone formation causes the evclu on 01- a considerable volume of carbon dioxide Thisgasma beallowedtoescapeu;

ecasing,orthe attermaybecaptmd o thereby creatififi: igas pressure w: n the well which a forcing the acid into the pores and crevices oi the rock. Aiter the action of the acid has practicallglceased the spent solution ccntsinin the mind salts may be umped or ball out. In many cases it may desirable to repeat the treatment one or more times. By making successive additions of smaller amounts of acid solution and pumping out the spent acid between a-Ereater cumulative eflect maybecg uced anbytheuseoiasingle larger args. It is not necessary, however, to add the acid solution through the pump tu as any other convenient way may be emp oyed. For instance, the pump tube may theth be withdrawn and a dump bailer used to lowor a charge of acid into the base of the bore.

In the ract'ical use of our method in the central chigan oil field, where the oil is derived from a calcareousrock formation, l

we have successfully used hydrochloric acid solutions of 10 to per cent strength to which was added a small amount,e. g. l to 5 per cent, of an arsenic compound. For example hydrochloric acid solution was added 2 gallone of arsenic acid solution containing 21 pounds of arsenic calculated as As- O,. The mixed solution was charged into an oil well through the iron pump tube, being followed by a quantity of crude oil to force the acid solution out of the tube into the well. After the acid was exhausted, it was pum ed out, and thereupon regular um ing 0 the oil was resumed. The to notion of the well was approximately oubled with one treatment.

The method has been used repeatedly for the treatment of low yield. or exhausted oil wells in producing territory with a resultant increase of output amountmg to as much as to 200 per cent, and in some cases wells which have ceased to flow have been brought back with a resumption of natural flow. Ihe treatment has been applied in the manner described without appreciable damage to the pump tube or well casing. The invention may also be employed similarly to increase the flow of gas wells and brine or water wells in cases where the mineral or water-bearing stratum, or the immediately adjacent strata, are of a limestone or calcareous formation, or of a nature such as to be acted upon and dissolved by hydrochloric acid solution.

Other modes of applying the rinciple of our invention may em loyed instead of 0 one explained, change eing made as rerds the method herein disclosed providcd' t e step or steps stated by any of the following claims or the equivalent of such stated etc or steps be employed.

e therefore particularly point out and distinctly claim as our invention 1. In a method of increasing the output of a well for producing a fluid mineral product such as oil, gas, water or brine, the ste which consists in introducin into the well an aqueous hydrochloric acid solution to which has been added a relatively small amount of an e nt capable of inhibiting action of the aci upon metals.

2. In a method of increasing the Output of a well for producing a fluid mineral p roduct such as oil, gas, water or brine, the step which consists in introducing into the well an A aqueous hydrochloric acid solution to which has been added a relatively small amount of an arsenic compound capable of inhibiting action of the acid upon metals.

8. In a method of increasing the output of to 4500 pounds of a 15 per cent Y Ill:

a well for producing a fluid mineral product such as oil, gas, water or brine, the ste which consists in mtroducin into. the we .a 5 to 20 per cent hydr oric acid solution to which-has been added from 1 to 5 per cent of an arsenic compound capable of inhibiting action of the acid upon metals.

4. In a method of increasing the output of a well for producing a fluid mineral product such as oil, gas, water or brine, the ste which consists in mtroducin into the we a 5 to 20 per cent hydroch oric acid solution to which has been added from 1 to 5 per cent of arsenic acid.

5. The method for increasing the output of an oil well which comprises introducing into the base of such well a5 to 20 per cent hydrochloric acid solution containing a relatively small amount of a corrosion inhibitor, permitting the acid to-act upon the rock formation surrounding the well cavity and with drawing the spent acid.

6. The method for increasing the output of an oil well which comprises introducing into the base of such well a 5 to 20 per cent hydrochloric acid solution containing a relatively small amount of an arsenic com ound capo: ble of inhibiting action of the acid upon metals, pcrmitting'the acid to act u on the rock formation surrounding the we withdrawing the spent acid.

7 The method for increasihgfhe output of an oil well which comprises introducing into the base of such well a 5 to 20 per cent hydrochloric acid solution containing-l. relatively small amount of a corrosion in 'bitor, permitting the acid to act u n the rock formation surrounding the we cavity while aggplying pressure upon the solution and wi drawing the nt acid.

8. The met ed for increasin the output of an oil well which comprises arging into the pump tube a quantit of a to per cent hydrochloric acid so ution containing a relatively small amount of a corrosion inh ibitor, expelling the acid from the tube into the bore of the well by applying pressure thereon, permitting the aci to ac u n the rock formation surrounding the w cavity and withdrawin the spent acid.

The math for mcreasin the output of an oil well which comprises arging into the pump tube a quanti of a 5 to 20 per cent hydrochloric acid so ution containing a relatively small amount of a corrosion mcavity and.

chloric acid solution to which has been added a relatively small amount of an organic nitrogen base capable of inhibiting action of the acid upon metals.

11. In a method of ia'eati a well for producing a fluid mineral P not such as oil,

, water or brine the step which consists in mtroduci into the well an aqueous hydrochloric aci solution to which has been added a relatively small amount of an organic sulphur compound capable of inhibiting action of the aci upon metals.

Signed by us this 24 day of June, 1932.

- JOHN J. GREBE.

ROSS T. SANFORD.

hibitor, expelling the acid from the tube into the bore of the well by a plyin pressure thereon, permitting the aci to ac u n the rock formation surrounding the we ca'vi under pressure due to the gas genera thereb and withdrawing the spent acid.

19. n a method of trea a well for producing a dud mineral uct such as oil,

as, water or brine the p which consists in introducing into th o well an aqueous hydro- Y D I 813 LA I M E R 1,877,504.John J. Grebe and Ron T. Sanford, Midland, Mich. TREATMENT or DEEP ,Wlm. Patent dated Sept. 13, 1932,. Disclmmer filed Apr.- 2, 1945, by the ueignee, The Dow Clumiml Company. Hereby enters this disclaimer to claims 1 to 9 inclusive, of said patent.

[Ofim'al Gazette May 1, 1945.] e 

